1. Field of the Invention
The invention relates to a process for manufacturing a pressed-in torsional vibration damper.
2. Description of Related Art
Pressed-in torsional vibration dampers generally consist of two metal rings arranged concentrically and spaced apart from one another, and an elastomeric spacer ring pressed into the annular gap, such that contact surfaces are formed between the metal and elastic components. The elastomeric spacer ring joins the flywheel ring to the hub ring arranged concentrically therewith, and damps the mutual torsional vibrations of the metal rings during operation. Accordingly, the invention also encompasses analogously configured annular components which damp torsional movements, such as rollers, ultra sleeves, and spherical bearings.
The spacer ring, which has a radial overdimension, is installed in the annular gap provided therefor between the metal rings by means of an application of force (insertion) parallel to the torsional vibration axis, such that the spacer ring is pressed into the gap. A torsional vibration damper of this kind is described, for example, in DE-OS 38 25 062.
Ordinarily, the available annular gap compresses the spacer ring, when it is pressed in, to 60% of its original radial thickness. This results in a defined stiffness of the elastomeric ring and thus a resonant frequency of the spring/mass system in the torsional vibration damper which cannot be decreased without, for example, enlarging the annular gap, which in most cases is impossible because the installation dimensions are predetermined.
Attempts to decrease these resonant frequencies simply by means of softer compliance, ie. via a lower radial compression pressure for the spacer ring, have been unsuccessful due to its incomplete static friction at the hub and flywheel rings due to insufficient radial pressures, especially after extended operation.
In ELASTOMERICS (January 1982), pp. 21-23, N. Hofmann and R. Riege propose a relevant rubber-metal adhesive joint such that the rubber surfaces of the spacer ring are precleaned with halogenated chlorohydrocarbons. The metal surfaces are also precleaned by using steam or chemical agents to remove grease.
The contact surfaces of the metal rings and/or of the elastomeric spacer ring are then given a film of adhesive, using an adhesive that is dry during assembly of the vibration damper and subsequently receives its adhesive ability by being post-vulcanized at, for example, 250.degree. F. (121.degree. C.) for 15 minutes. During this post-vulcanization the parts being adhesively bonded must be kept under radial pressure, which depends on the Shore hardness of the elastomeric ring.
In practice, however, this process yields satisfactory adhesive strength only above 150.degree. C. and after 30 minutes.
Another disadvantage of heat-treated, or "post-vulcanized," adhesives is that the geometrical arrangement of the hub, elastomeric, and flywheel rings can change due to the extreme heat treatment, so that the components must be immobilized during adhesive bonding. This action, and the heat treatment, inherently produce a bottleneck in the production sequence.